I have been asked so many times why tire pressure is so important.  I hope this brief write up answers some of your simple questions.  The following web page goes into great detail about tires. 

www.carbibles.com/tyre_bible.html

Believe it or not, a person could talk for hours about tires.  They can tell you a great many things about the condition of the car and the driver’s driving style.

To achieve the best fuel economy, handling, and safety, tires must be inflated to the proper tire pressure.  The proper inflation pressure will allow the tire to have the most effective "contact patch", the amount of tire touching the pavement and will allow the sidewalls of the tire to withstand the weight of the car and cornering forces.  In addition, the proper “contact patch” allows the tire to achieve the best traction which allows the braking system to work most efficiently.

I would like to just say one last thing about tires.  They are the only thing between you and the road.  You could have the best handling car from the suspension point of view, but if your tires are not up to specification or poorly maintained, your car will handle like a dog on a wet floor.

Tire Care

• To determine the proper tire pressure, look at the sticker on the driver side door jam of your car or in the owner’s manual.  If you have gone with high performance tires or have gone with a different tire specification, i.e. wider tire, different aspect ration, etc..., I suggest you talk to a qualified tire technician or go with the tire manufacture’s recommendation to determine the proper tire pressure for your needs
• Be sure to check your tires at least once a month.  I personally visually look at my tires as I approach my car to get into it.  I do this since my tires seem to be magnets for nails and screws.
• Each time you check your tires, look at each tire looking for nails, non-uniform wear, or cracks.  If you notice anything, it is suggested you have a qualified mechanic check it out.
• Use a quality tire gauge.  Many web sites and reference materials indicate using a tire pressure gauge costing around $5-$10.  I suggest not going with a cheap tire gauge.  I had a neighbor that could not figure out why his car kept telling him that his tires did not have enough pressure.  I put my quality tire pressure gauge on his tires and he found out his ‘cheap’ gauge was around 5 psi off too low.  As for me, I spend no less that $20 on a tire gauge.  Gauges of this quality are easy to read, have rubber around the gauge, and have long hoses.
  
• Rotate your tires every 5000 miles.  Please consult your owner’s manual for the proper tire rotation procedure.  If you have gone with high performance tires or have gone with a different tire specification, I suggest you talk to a qualified tire technician or go with the tire manufacture’s recommendation to determine the proper procedure.  Be sure to properly torque the lug nuts as well.  To determine the proper torque specifications, please consult the appropriate shop manual.  In addition, many times you can find out the appropriate torque value online, be sure that you trust the web site.
• Be sure to check your spare tire as well

Tire Wear Patterns Tells A Story

	Tires not having too little pressure cause the middle of contact patch to arch up.  This causes both outside portions of the tire to contact the pavement.  In addition, the sidewalls of the tire cannot maintain stability of the tire.  This affects handling and stability of the car.
Tires having too much pressure cause the middle of the tire to bulge out.  This reduces the contact patch since the edges of the tire are pulled back.  This affects tractions since less tire is actually touching the road.
	Tires with uneven wear indicate suspension issues or alignment problems.  If you notice an uneven wear pattern, it is suggested you have a qualified mechanic examine your car to determine the root cause.